[Kuritza]

Oh come on. Marverni, weak?

Their units can be easily massed, and they are actually quite tough for a cannon fodder they are. Good combat stats, decent damage.
What makes Marverni strong is mages. Easy access to gifts from haven - trust me, its awesome. Also nice and easy soul slay vs Thugs/SCs and bladewind vs hordes. What else would you wish for?
Oh yes, ashaic record + early age = lots of gems. Access to water magic = sea king's court, very good thug, perhaps even SC. Nature magic = rings of regeneration and vine shields (though you might want to trade a booster or empower, that 10% to get a nature pick on mages doesnt work EVER, I hired over 40 of them and no one had N2. Must be a bug.)